<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>HTMLs History APIs</title>
    <link rel="stylesheet" href="./common.css">
</head>
<body>
    <!-- 
        domain , 组织文件，向用户提供很多资源
        链接把资源组织起来 
        网站--一切皆资源  Restful
    -->
    <div class="wrapper">
        <ul class="nav">
            <li><a href="index.html">Home</a></li>
            <li><a href="fluffy.html">Fluffy</a></li>
            <li><a href="socks.html">Socks</a></li>
            <li><a href="whiskers.html">Whiskers</a></li>
        </ul>
        <p class="content">Welcome to Kittens! Home of Fluffy, Socks, and Whiskers. If you're not suffering from a cute overdose within the hour, then you really are a heartless bugger! Now lets look at some cats!</p>
        <div class="media">
            <img class="photo" src="http://www.ichong123.com/uploads/2014/08/m1.jpg" alt="">
            <!-- <img class="photo" src="http://www.ichong123.com/uploads/2014/08/m1.jpg" alt="index" > -->
        </div>
    </div>
    <script>
        //传统web网站 发起优化
        // ajax 刷新整个页面 不用白一下
        function getHtml(href,callback) {
            // fetch 小弟
            const xhr = new XMLHttpRequest(); // web 2.0
            xhr.open("GET",href);
            xhr.send(); // 发送请求
            xhr.onreadystatechange = function() {
                console.log(xhr.readyState);
                if(xhr.readyState == 4){ //服务器响应 完全到达
                    // console.log(xhr.responseText);
                    callback(xhr.responseText);
                }
            }
        }

        function createState(data) {
            // . 可以匹配任何字符
            // + 匹配一次或多次
            // () 分组
            const contentMatches = data.match(/content">(.+)</);
            // console.log(contentMatches);
            const content = contentMatches[1];
            // console.log(content);
            const photoMatches = data.match(/img.+src="(.+)"\s/);
            const photo = photoMatches[1];
            // console.log(photo);
            return {
                content,
                photo
            }

        }
        // 生命周期 资源加载完自动触发
        window.addEventListener('DOMContentLoaded',function(){
            // 完成html+css页面渲染
            // 比load 更早的js运行，交互
            const links=document.querySelectorAll('.nav li a');
            links.forEach(link =>{
                link.addEventListener('click',function(event) {
                    event.preventDefault();
                    let href=event.target.href;
                    // const xhr = new XMLHttpRequest();
                    getHtml(href,function(data){
                        // callback
                        let state = createState(data);
                        // console.log(state);
                        document.querySelector('.content').innerText=state.content;
                        document.querySelector('.photo').src=state.photo;
                        console.log(state);
                    })
                })
            })
        })
        // window.addEventListener('load',function(){
        // })
    </script>
</body>
</html>